Not only will landlords save on repainting and other maintenance costs, they may also save on their fire insurance.  Since smoking related materials are the number one cause of fires, many insurance companies offer discounts for smoke-free policies.   Resale values of smoke-free buildings can also be higher.  Prohibiting smoking outdoors or restricting smoking to designated areas reduces cigarette butt litter. 

Source: Federal Emergency Management, U.S. Fire Administration/National Fire Data Center, Residential Smoking Fires and Casualties, Topical Fire Research Series, Volume 5-Issue 5 (June 2005). NY Times, "Real Estate & Secondhand Smoke: On Tobacco Road, It's a Tougher Sell," February 8, 2004